Focus an interactive element by its index in the page. Indices are returned by getPageInfo. This is the preferred method for focusing text input fields before typing. Always check the page info after focusing.
AI agents invoke focusElementByIndex to trigger actions in Chrome MCP Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
Focusing an element triggers browser-level interaction via Chrome DevTools Protocol, which constitutes an external browser action. While focusing alone has limited direct impact, it manipulates the browser's DOM state and is typically a precursor to further input actions. It falls under Execute as it triggers external browser operations rather than simply reading data.
From the tool's definition Focus an interactive element by its index in the page... preferred method for focusing text input fields before typing
Documented attack patterns abuse exactly the kind of access focusElementByIndex gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Chrome MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for focusElementByIndex:
{
"version": "1",
"default": "deny",
"tools": {
"focusElementByIndex": {
"limits": [
{
"counter": "focuselementbyindex_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}focusElementByIndex stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
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Focus an interactive element by its index in the page. Indices are returned by getPageInfo. This is the preferred method for focusing text input fields before typing. Always check the page info after focusing. It is categorised as a Execute tool in the Chrome MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Chrome MCP Server MCP server in PolicyLayer and add a rule for focusElementByIndex: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Chrome MCP Server. Nothing to install.
focusElementByIndex is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the focusElementByIndex rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for focusElementByIndex. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
focusElementByIndex is provided by the Chrome MCP Server MCP server (lxe/chrome-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Chrome MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
11 Chrome MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.